$h/e$ Oscillations in Interlayer Transport of Delafossites

TL;DR

This study reveals a novel quantum interference effect in layered delafossites, showing $h/e$ oscillations in out-of-plane magnetoresistance that persist over large scales and high temperatures, indicating extraordinary quantum coherence.

Contribution

It reports the discovery of $h/e$ oscillations in delafossites, demonstrating a new form of quantum interference due to periodic field-modulation of out-of-plane hopping.

Findings

$h/e$ oscillations observed in layered delafossites.

Quantum coherence persists over 10 micrometers and above 50K.

Standard Aharonov-Bohm explanation does not apply.

Abstract

Transport of electrons in a bulk metal is usually well captured by their particle-like aspects, while their wave-like nature is commonly harder to observe. Microstructures can be are fully designed to reveal the quantum phase, for example mesoscopic metal rings resembling interferometers. Here we report a new type of phase coherent oscillation of the out-of-plane magnetoresistance in the layered delafossites PdCoO$_2$ and PtCoO$_2$. The oscillation period is equivalent to that determined by the magnetic flux quantum, $h/e$, threading an area defined by the atomic interlayer separation and the sample width. The phase of the electron wave function in these crystals appears remarkably robust over macroscopic length scales exceeding 10$\mu$m and persisting up to elevated temperatures of $T$>50K. We show that, while the experimental signal cannot be explained in a standard Aharonov-Bohm analysis, it arises due to periodic field-modulation of the out-of-plane hopping. These results demonstrate extraordinary single-particle quantum coherence lengths in the delafossites, and identify a new form of quantum interference in solids.